Concrete inserts are used to connect items to concrete structures after the concrete has been poured and hardened. A typical use of an insert is to embed it in a concrete ceiling so that an anchor bolt may support a pipe hanger or the like to the ceiling after the concrete hardens. The following description will concern inserts embedded in ceilings although the inserts of this invention may also be embedded in concrete floors or walls.
Some prior art inserts are U-shaped sheet metal pieces with legs terminating in flanges that lie in a common plane and with a bridge between the legs having a hole in it through which a threaded fastener is inserted. An internally threaded coupling is positioned between the legs of the U-shaped piece to butt against the bridge, and a threaded fastener is screwed into the internal threaded cavity of the coupling and locked in place with a nut that abuts the bridge. Concrete inserts of this nature are known, a typical example of which is illustrated as item 276 on page 89 of the 1986 catalog published by Kin-Line, Inc., located at 6425 San Leandro Street, Oakland, Calif. 94614. An improved version of this type of insert is disclosed in U.S. Pat. No. 5,205,690. A problem with inserts of this type is that if metal forms are used that are not stripped after the concrete hardens, holes for support rods must be drilled before concrete is poured and the insert bridges the holes in the form so that the concrete, before it sets, can flow into the hole unless measures are taken to prevent that flow. Additionally, the bridge of the insert must be aligned with the hole in the form through which a threaded support rod passes, and that alignment must be maintained during the concrete pour if the support rod is to be vertical after the concrete hardens.
Other inserts are simply elongated metal pieces from which support rods extend, the elongated metal pieces having legs that hold a bridge high enough above the form so that poured concrete may flow beneath the bridge to hold it firmly after the concrete hardens. A typical insert of this type is #370 Metal and Concrete Insert manufactured by Michigan Hanger Co., Inc. of Niles, Ohio and illustrated on page 35 of Price List No. 291 published by that company. This type of hanger is extremely unstable prior to and during a concrete pour and cannot be used with a wooden form because use of a wooden form requires a threaded element that is flush with the concrete ceiling after the form is removed.
Another prior art concrete insert is typified by FIG. 109EZ of the Tolco Incorporated catalog published Nov. 1, 1994. The 109EZ insert is illustrated on page 68 of that catalog and a similar insert identified as a 109 insert is illustrated at page 69 of that catalog. Both illustrated inserts have an L-shaped threaded rod that extends through a metal piece bridging two of the lands of a corrugated metal form. The illustrated inserts cannot be used with wooden forms, and when they are subjected to heavy loads the L-shaped rods tend to straighten and extrude out of the ceiling. In addition, the hole in the metal form through which the support rod extends must be protected from leaking concrete during the pour, and the insert is unstable during a concrete pour so that it can be tilted with the result that the support rod will not be vertical after the concrete hardens. Both of the above-noted inserts are illustrated on page 89 of the Kin-Line, Inc. catalog, copyrighted 1986. Item 276 on that page is a spot insert such as described above which is useful only with wooden forms, while item 293 is the L-shaped support rod that is useful only with metal forms.